1. Field of the Invention
The present invention relates to a photovoltaic conversion device which is easy to manufacture and has high photovoltaic conversion efficiency, an optical power generator and a manufacturing method of the photovoltaic conversion device.
2. Description of Related Art
A photovoltaic conversion device such as a solar cell and an optical sensor serves to transform optical energy such as sunlight incident on its surface into electric energy. In this photovoltaic conversion device, it is considered that its photovoltaic conversion efficiency is improved by reducing loss of incident light and generated photocurrent.
Especially to reduce loss of photocurrent, it is effective to reduce recombination of carrier on a surface of a semiconductor for performing photovoltaic conversion by forming a protective film on the surface of the semiconductor (Refer to “Fundamental and Application of Thin Film Solar Cell”, the 1st edition, written and edited by Makoto Konagai, OhmSha, Ltd., Mar. 20, 2001, pp. 53 to 55).
Since only a small amount of semiconductor as a material is used, the photovoltaic conversion device using a semiconductor particle among photovoltaic conversion devices has attracted much attention in recent years.
For example, as the photovoltaic conversion device in which a protective film is formed on the semiconductor particle, there is proposed a micro photovoltaic cell in which a cathode and an anode are each formed at a bottom part and a top part, respectively, of a spherical semiconductor device on which a protective film of silicon oxide is formed, both parts being opposed to each other across the center of the semiconductor device (Refer to Unexamined Patent Publication No. 2001-274439).
Generally, in the photovoltaic conversion device using the semiconductor particle, since an individual photovoltaic conversion device generates only a small amount of electric power, a lot of photovoltaic conversion devices are joined to a substrate or the like and the cathode/anode of one photovoltaic conversion device is the anode/cathode of another photovoltaic conversion device through a conductor to generate a large amount of electric power.
However, when a lot of micro photovoltaic cells are joined to the substrate or the like, electrodes of the micro photovoltaic cells must be neatly aligned. Accordingly, to use the above-mentioned micro photovoltaic cell, there is a disadvantage that manufacturing is difficult and production efficiency is low.
To form the cathode and the anode in the above-mentioned micro photovoltaic cell, it is necessary to mask each of the semiconductor particles with a corrosion-resistant photosensitive resin film and form a contact hole for cathode and a contact hole for anode. When such spherical semiconductor particle is masked, a complicated process is required. For this reason, the production efficiency is remarkably low and the high-quality of the micro photovoltaic cell thus obtained is hard to be maintained.
An object of the present invention is to provide an easy-to-manufacture, high-quality photovoltaic conversion device and an optical power generator and also to provide a manufacturing method of the photovoltaic conversion device with high production efficiency.